1. Field of the Invention
The present invention relates to an ultrasonic microscope.
2. Description of the Related Art
An ultrasonic microscope is known in which a sample is two-dimensionally scanned with an ultrasonic beam, and the waves passing through, or reflected from, the sample are processed to form an image of the sample. Ultrasonic microscopes of this type are disclosed in various publications, such as Published Examined Japanese Patent Application No. 59-44582 and Published Unexamined Japanese Patent Application No. 58-196453.
In these microscopes, that surface of a sample which is to be scanned with an ultrasonic beam must be substantially parallel to the focal plane of the acoustic lens which focuses the beam onto that surface of the sample, in order to form a clear image of the sample. Published Unexamined Japanese Patent Application No. 62-249052 discloses an ultrasonic microscope which can be so adjusted that the scanning surface of the sample is substantially parallel with the focal plane of the acoustic lens. This microscope includes a vibrator and a goniometer. The vibrator can vibrate the acoustic lens in one direction. The goniometer is used to support a sample, and has a mechanism for adjusting the inclination of the sample in both an x-direction and a y-direction. Either the vibrator or the goniometer is rotated in the x-y plane, thereby changing the direction in which the acoustic lens vibrates. The inclination-adjusting mechanism is operated to distribute the intensities of the ultrasonic beams reflected from the sample, uniformly in the direction in which the acoustic lens vibrates. When the intensities of the ultrasonic beams are distributed uniformly in this direction, the scanning surface of the sample and the focal plane of the acoustic lens are substantially parallel to each other.
The ultrasonic microscope disclosed in Published Unexamined Japanese Patent Application No. 62-249052 is complex, not only because the goniometer has a mechanism for adjusting the inclination of the sample in both the x-direction and the y-direction, but also because the goniometer or the vibrator for vibrating the acoustic lens is rotated in the x-y plane in order to adjust the inclination of the scanning surface of the sample. Further, it is time-consuming to successfully adjust the inclination of the scanning surface of the sample. There is another problem with this ultrasonic microscope. When cryogenic liquid, such as liquid nitrogen, liquid argon, or liquid helium, is filled in the gap between the acoustic lens and the sample and used as a medium for transmitting the ultrasonic beam, it is necessary to locate both the acoustic lens and the goniometer within an adiabatic vessel. This makes it even more difficult to adjust the inclination of the scanning surface of the sample.